Hey, In 3 months I will officially be a mechanical engineer. However there are some things that my university did not clarify enough. Mostly because some of our books aren't well written. I have some subjects, which I think I should know more about. So as preparation to my first job, I would like to educate myself a bit more. What I'm searching for in the following questions is a recommendation for a good book, a site or a program which clarifies/solves each specific problem. The cost of the books is not a real factor for me, as long as it is a good book . I can read English, German and Dutch. Questions about mechanical design: a good book about force calculation (in a gearbox). e.g. diametersize of the shafts?, how many bolts and what size do I need to seal a flange?, ... a good program about force calculation (in a gearbox). Answer: SIMPACK, Kissoft, ... ? How to chose the best material for your application? Material science book? I know enough about materials, but there's a difference between knowing and actually choosing them. Is there a guideline for this? How to chose the best electrical motor? e.g. with or without gearbox, induction, ... ? Is there a guideline for this? Electromotor book? An overview and clarification about all the types of norms: e.g. EN ISO DIN, ... Introduction to CAM How to determine the tolerances in a design? A good book about tribology in mechanical design. A book about plastic molding What's a good magazine/blog/forum to read to be up to date in mechanical/production design (other then the mechanical design forum)? Are there any other subjects that most beginning engineers don't know, which would be handy? Any suggestions? I hope this is the right place to ask these questions. If you want I can also put each question in a separate thread? Thank you!
This is pretty dependent on what kind of job you are going to have. It will be impossible to be an expert on all aspects of mechanical engineering. In the first months of your job you will need to learn more about the industry/product specific aspects. The best preparation for finding a job is focussing on how you're gonna show that you are a good mechanical engineer.
Maybe a better title would be: "Beginning engineer: a search for/ guide to knowledge". The questions aren't only as preparation for a job. They are also just out of interest. I'm not searching to become an expert. I just want to be able to know where to look when these questions arise. I have had these questions for quite some time now. Sadly I have yet to find a good way to solve them. Thanks for the reply!
A lot of companies have their own internal design standards - so when you get a job (assuming it is with a professional company and a company that is reasonably big) - then you will be guided by your superiors on a lot of the "issues" you have raised, and you will also be given guidelines on how things have to be designed - to satisfy the company's own rules. Some of the issues you have highlighted above - are somewhat specialized - and will depend on the application - for example your question about electric motors. In some applications a DC brushed motor will fit the bill - and in other applications a DC brushless motor will be more suitable. In many applications - several different types of material will be suitable - but the cost of the material, and the cost of machining or forming or joining the material may be factors - but again this will have to be weighed up against the type of product that this part is going to be used in - and whether the product is going to be low, medium or high volume - but also whether the customer may be willing to pay more money for the product. You can see examples of this in the car industry, where some customers are willing to pay £100K plus for a composite construction car - but that doesn't mean to say that a composite construction car is any better than a steel car!! Again you could say exactly the same about an ordinary bicycle - my one is steel - but a lot of manufacturers have used aluminium - and just "google" cracks in aluminium bicycles - and you will see lots of cracks in them - but you will not find any in my steel bike - so why aluminium - because it does not rust - like my steel one will eventually rust - and my steel one is lighter than the aluminium bikes too!! So these days the look of things is perceived to be everything. A colleague of mine has a carbon fibre bike - and you might think that that is the greatest thing since sliced bread - well no - since his diagonal tube snapped - which is something that has never happened on my steel bike - ever!! I am not sure where you are from - but with your linguistic skills - I would probably look for a job in Germany - since they are very good on engineering - and I would probably spend more time looking for a good boss than a good book - since they are much better value!! Hope this helps.
As others have said above, much of what you're looking for is the kind of thing you learn on the job, with the specifics depending on where you're working and the manufacturing facilities available. But for example, "best material": Say you're making a simple bent bracket. It could be a variety of different materials. Perhaps it should be, say, 3/32" steel. If you're mass producing them, you might do that, and plate or or paint them. But if you're making only a few of them, it might make more sense to use stainless steel (even though the material itself is more expensive) and not have to plate them... or if your shop doesn't have a bending brake, you might make it out of a thicker aluminum extrusion. Or you might use 1/8" stock because you use lots of it elsewhere. Often there is no "best" material, but there might be a most "convenient" material. Or tolerances: Lots of even experienced engineers struggle with this. You can calculate every tolerance to insure all parts will always fit together. In some cases, this is necessary, but the parts will likely cost a lot more. Or you might leave it looser, and parts will "usually" fit together, with the occasional hand fitting necessary, and the overall cost will be lower. Again, where the line is drawn will depend on where the parts will be made. As an example, I do occasional consulting work for a small machine shop. By happenstance of the shop's history, they have some high accuracy jig grinders and jig borers. I can design parts for them with extremely close tolerances what would be unreasonable for other shops I've worked for, because they can easily meet those tolerances, for them it doesn't add extra cost. For much engineering work, you don't even worry about tolerances because modern manufacturing methods can easily make parts more accurately than necessary (but you do need to be aware of where tolerances do need to be specified). Gearbox internals: Either you'll work for a company that builds gearboxes, in which case you'll be working from the company's existing designs and standards and have guidance from other engineers, or you're buying a gearbox, getting the information from the manufacturer's catalog. The same for many other components (bearings, motors, cylinders, pumps, etc.). Most catalogs have a wealth of engineering information. Machine Design and Design News magazines are worth getting (and they're free).
Ok, so most of my questions will be answered when I get a job. I knew it had a lot to do with experience. Even so if you have recommendations for some books, I'll gladly read them. The reason why I mention a gearbox is solely, because for my master's thesis I'm designing one :-D. For instance the tolerances: the ones I use should be ok. But I have constantly the feeling that I made a mistake somewhere. Because sometimes I'm just kind of guessing... The same with the motor. I'm sure it's a good motor, because I asked an assistant to help me with choosing one. If I would have chosen it by myself, it would probably have been a very similar one. But I would have had the feeling that I kinda guessed. There are so many to choose from. I know engineering is a lot of calculated guessing . It just surprises me every time how much a lot is. Thank you for the recommendation for the magazines!! I'm from Belgium btw. I'm searching for work in a French (design) company to strengthen my French. Thank you!!
I used Shigley's Mechanical Engineering Design in school for one of my classes and have referenced it on multiple occasions during design work. I would describe it as covering failure theories for mechanical parts. I am a recently graduated engineer so i don't have the years of experience but I have heard others mention this book. Machinery's Handbook is always a great reference. It contains a vast amount of information for anyone working in a machine shop or designing parts that will need to be made in a machine shop. My other recommendation is to make friends with people who have experience whether that be engineers or machinists. I have learned a lot by asking questions and looking at work others have done. I find myself picking up random objects and trying to figure out how they were made and why they were designed they way they were, you can learn from others work this way and discover ways of solving problems you might not have thought of. you might even discover problems you wouldn't have thought about but were addressed in the design. As i think you realize engineering problems are so varied it is difficult to put all the answers in a book. In my opinion thats why engineering is fun ... we get paid to think not follow directions.
In most cases, a tolerance analysis is only required on a few places within a subassembly. There are two types of clearances: those that do not justify a tolerance analysis. And those that do. Case 1) After working in design for a while, you will be able to adjust most clearances to be beyond reasonable, allowing you to use engineering judgement to bound the problem and not perform the analysis. You make all gaps as large as possible, and go through your design piece by piece looking for places that are "tight". Go through it in assembly sequence, with an out for how the part will be installed, considering viewing angles, finger and tool access, and even how the installer will be able to adjust the part while trying to install it. Also consider its operational clearances. When it's working, what moves where, and how much closer could it reasonably get? Keep the clearances large enough to where it would be an obvious waste of time to perform a tolerance analysis on such a large gap. This type of engineering judgement comes with time and is not limited to tolerances, but also applies to thermal, structural, dynamics, and other analyses/evaluations. Case 2) Sometimes making a clearance large is not an option. For example, mating parts have to have pre-determined physical contact. Or, the designing in a relatively "small" volume. In this case, a tolerance analysis may be required. The vast majority of the time, if you have given some thought to how your system is to be built and operated, you should be able to do some simple hand calculations to determine your tolerances. I'd suggest a spreadsheet to calculate and track your tolerances and critical gaps. Try http://www.quicktol.com for an Excel-based tolerance analysis tool to use. I'd also recommend a simple(!) and short tolerance analysis book like "Make It Fit" on Amazon. -Jason http://www.quicktol.com
Wauw ok, thanks for the recommendations . I should have said I'm used to the metric system. So I'm not sure if I'm going to buy Shigley's Mechanical Engineering Design, Machinery's Handbook. I'll look into it at the beginning of August. That's when I'll be done with my exams and will have a bit more time for research. I'll look into to quicktol and make it fit as well. Thanks again, Koenraad
